This invention relates generally to radio frequency (RF)/microwave circuits, and in particular, to a unique four-way power combiner/splitter.
Power combiners and splitters have many applications in the RF/microwave field. They are particularly useful in power amplification applications. For example, often an input signal to be amplified is split using a power splitter into several components and applied separately to a plurality of amplification stages. Each of the amplification stages amplifies each of the components of the input signal. Then, the amplified components of the input signals are applied to a power combiner to recombine the amplified components into a relatively higher power and gain output signals.
Prior art power combiners and splitters typically operate over a relatively narrow bandwidth. This is because many prior art power combiners and splitter use transmission lines of particular electrical lengths to adjust the phases of the signals so that the signals are properly combined or split. Since the electrical length of a transmission line is dependent on the frequency of the signal, these prior art combiners and splitters do not work well with frequencies outside the intended operating frequency. As a result, most prior art power combiners and splitters have relatively narrow bandwidth.
Thus, there is a need for a power combiner and splitter that does not depend on a transmission line or lines being a particular electrical length in order to provide much greater operating bandwidths. Such a need is met by the invention described herein.
An aspect of the invention includes a four-way power combiner/splitter that includes a first transmission line having a first non-grounding conductor and a first grounding conductor, wherein the first grounding conductor is grounded at a first end of the first transmission line. The combiner/splitter also has a second transmission line having a second non-grounding conductor and a second grounding conductor, wherein the second grounding conductor is grounded at a first end of the second transmission line. The non-grounding conductors of the first and second transmission lines are electrically coupled together at the respective first ends of the first and second transmission lines. An output/input port is provided that is electrically coupled to the first and second non-grounding conductors at the respective first ends of the first and second transmission lines. Additionally provided are a first input/output port electrically coupled to the first non-grounding conductor at a second end of the first transmission line, a second input/output port electrically coupled to the first grounding conductor at the second end of the first transmission line, a third input/output port electrically coupled to the second non-grounding conductor at a second end of the second transmission line, and a fourth input/output port electrically coupled to the second grounding conductor at a second end of the second transmission line.
The four-way power combiner/splitter may include a first impedance element electrically connecting the first and second non-grounding conductors at the respective second ends of the transmission lines, and a second impedance element electrically connecting the second and fourth grounding conductors at the respective second ends of the transmission lines. The first and second impedance elements are selected to improve the balance of currents flowing through the first and second transmission lines. In addition, the four-way power combiner/splitter may include first and second ferrites coupled respectively to the first and second transmission lines to increase the effective electrical lengths of the lines. The transmission lines each may be configured into a twisted pair of wires, a coaxial transmission line, a microstrip, a striplines, or other forms of transmission line mediums.